This Standard provides for the safe design of powered platforms for building maintenance,where window cleaning and related services are accomplished by means of suspended equipmentat heights in excess of 35 ft (11 m) above a safe surface, e.g., grade, street, floor, or roof level.

The provisions of the Standard are intended to apply to all known systems used to supportsuspended maintenance equipment as well as the suspended equipment itself (either permanentlyinstalled or transportable equipment). Guidelines are also included for a building’s structuralsupport areas as well as the building surfaces that actually interface with the equipment.

The Standard does not apply to other suspended powered platforms used for remedial renovationsor modifications to buildings. The safe use of these types of scaffolds is addressed byAmerican National Standard ANSI A10.8. The A120.1 Standard also does not relate to any serviceperformed by persons supported by equipment covered by any of the ANSI A92 standards.The purpose of this Standard is to ensure the protection of all powered platform users as wellas persons potentially exposed to use of the equipment. In developing this Standard, safety hasbeen held as the primary consideration. The Standard requires that permanently installed ortransportable equipment be properly designed by a qualified professional engineer, taking intoaccount specific building features rather than attempting to accommodate the system to a building’sstructure and facade features that may not be suitable for its safe operation. In addition,care has been taken so as not to exclude or render obsolete any existing product or equipment.

This Standard reflects the evolution of a project begun in 1962 by the American NationalStandards Committee on Window Cleaning Safety, A39. At that time, the Committee recognizedthat a new method was being developed for cleaning fixed sash windows by means of a specialscaffolding. In order to deal expertly with this new development, a new project was established,separate from that handled by the A39 Committee. Following a general conference, the AmericanNational Standards Committee on Powered Platforms, ANSI A120, was formed, with the NationalSafety Council acknowledged as sponsor. In 1965, The American Society of Mechanical Engineerswas approved as cosponsor. In 1984, the Building Owners and Managers Association Internationalwas approved as Secretariat.

A previous edition of the Standard, A120.1-1970, was administratively withdrawn in 1989. ThisStandard had established safety requirements for the design, construction, installation, inspection,and use of power-operated platforms for exterior building maintenance. The Standard did notapply to temporary equipment used for construction work or to devices raised and loweredmanually.

A120.1-1992 was the result of joint action by participating organizations under the auspices ofthe American National Standards Institute. That Standard was approved through two votes ofthe ANSI A120 Committee, at a meeting in New York City (October 17, 1991) and by letter ballot(dated December 30, 1991).

In 1995, ASME again assumed sponsorship of the Standard. ASME A120.1-1996 was approvedby ANSI on April 17, 1996. ASME A120.1-2001 was approved by ANSI on July 3, 2001. ASMEA120.1-2006 was approved by ANSI on September 20, 2006.

This revision was approved by the American National Standards Institute on July 16, 2008.